FIG. 1 is a schematic diagram of the overall architecture of a long-term evolution (LTE) system in the related art, and as shown in FIG. 1, the LTE architecture comprises: Mobility Management Entity (MME), Serving GetWay (SGW), user equipment (UE) or it is called as terminal, and eNodeB (referred to as eNB), and the UU interface is between the UE and the eNB, the S1-MME (S1 for the control plane) interface is between the eNB and the MME, the S1-U interface is between the eNB and the SGW, and the X2-U (X2-User plane) and X2-C(X2-Control plane) interfaces are between the eNBs.
FIG. 2(a)˜FIG. 2(d) are schematic diagrams of a protocol architecture of the control plane and the user plane between the UE, the eNB and the core network (MME or SGW) in the LTE in the related art, as well as a protocol architecture of the control plane and the user plane between the eNB and the eNB, as shown in FIG. 2(a)˜FIG. 2(d),
In the LTE, the interfaces between the UE and the eNB from bottom to top can be divided into the following protocol layers: Physical (PHY) layer, Media Access Control (MAC) layer, and Radio Link Control (RLC) layer, Packet Data Convergence Protocol (PDCP) layer, and Radio Resource Control (RRC) layer. In the LTE, the user plane protocol stacks of the interfaces between the UE and eNB from bottom to top are divided into the following protocol layers: PHY, MAC, RLC, and PDCP. Wherein, the PHY layer is mainly set to transmit information to the MAC or higher layer via a transmission channel; the MAC layer is mainly set to provide the data transmission through a logical channel and be responsible for radio resource allocation and for achieving functions such as hybrid automatic repeat request (HARQ, Hybrid ARQ), Scheduling (SCH), priority processing and multiplexing/de-multiplexing (MUX); the RLC layer is mainly set to provide the user data and control data segmentation and retransmission services; the PDCP layer is mainly set to complete the user data transmission in the RRC or user plane; the RRC layer is mainly set to complete the broadcast, paging, radio resource control connection management, radio bearer control, mobility function, UE measurement report and control. In the LTE system, the UE can only transmit and receive data with one eNodeB, which undoubtedly limits the user throughput and mobility performance of the UE.
In the LTE, the protocol stack of S1-MME interface from bottom to top is divided into the following protocol layers: L1 protocol, L2 protocol, Internet protocol (IP), Stream Control Transmission Protocol (SCTP), and S1-Application Protocol (S1-AP).
In the LTE, the protocol stack of S1-U interface from bottom to top is divided into the following protocol layers: L1 protocol, L2 protocol, User Datagram Protocol/Internet Protocol (UDP/IP), GPRS Tunneling Protocol-User plane (GTP-U).
In the LTE, the protocol stack of X2-C interface from bottom to top is divided into the following protocol layers: L1 protocol, L2 protocol, IP, SCTP, X2-Application Protocol (X2-AP).
In the LTE, the protocol stacks of X2-U interface from bottom to top are divided into the following protocol layers: L1 protocol, L2 protocol, UDP/IP, GTP-U.
FIG. 3(a)˜FIG. 3(c) are respectively schematic diagrams of existing S1 interface, X2 interface and enhanced radio access bearer (E-RAB) setup processes, wherein the S1 interface setup process generally comprises: the eNB sending a S1 SETUP REQUEST message to the MME, and the MME returning a S1 SETUP RESPONSE message to the eNB. The X2 interface setup process generally comprises: the eNB1 sending a X2 SETUP REQUEST message to the eNB2, and the eNB2 returning a X2 SETUP RESPONSE message to the eNB1. The radio access bearer setup process generally comprises: the MME sending an E-RAB SETUP REQUEST message to the eNB, and the eNB returning an E-RAB SETUP RESPONSE message to the MME.
Currently, due to the scarcity of spectrum resources, as well as the surge of mobile users in services with massive flow traffics, in order to increase user throughput and enhance mobility performance, the needs of using high-frequency point such as 3.5 GHz for hotspot coverage are increasingly obvious, and using the low-power node becomes a new application scenario. However, since the high-frequency signal attenuation is relatively severe, the coverage range of new cell is relatively small and does not share stations with the existing cells, and if a user moves between these new cells, or moves between the new cells and the existing cells, it will cause frequent switching process, making frequent user information transfer between the eNodeB, thus causing a great signaling impact on the core network, and further curbing the introduction of a large number of small cell eNodeBs at the radio side.